1. Field of the Invention
The invention concerns a levelling shoe.
2. Description of Related Art
A levelling shoe of this type is prior art from, for example, CH-PS 652 186. This levelling shoe also displays a base plate and a supporting plate for an object, for example a machine or a device. The supporting plate can be displaced in a perpendicular direction relative to a base surface of the base plate by means of an adjusting wedge device. The adjusting wedge device comprises an adjusting wedge which in top view is essentially U-shaped, displaying a middle section and two wings which can be displaced by means of a screw spindle transversely to the vertical direction and is at the same time guided with a pair of lower supporting surfaces inclined towards each other on corresponding surfaces of the base plate. The direction of displacement of the adjusting wedge is inclined with respect to the base surface. Both the middle section and the wings are provided with upper supporting surfaces for the supporting plate, while these in turn form a pair of surfaces that are inclined towards each other. When the adjusting wedge is moved in one direction the supporting plate is raised, being impeded by a lateral stop element permanently connected to the base plate from moving transversely and is moved only in a perpendicular direction. When this occurs, especially when raising large loads, enormous lateral forces are exerted on the stop element, which can even cause breakage of the latter. The screw spindle and/or a bearing in which the screw spindle rests are also exposed to a powerful axial stress.
The U-shape of the adjusting wedge is necessary so that there is space on one side for the screw spindle and on the other for a connecting bolt arranged at a right angle to the base surface connecting the object with the base plate. Both the screw spindle and the connecting bolt, however, are located at a distance from a central plane perpendicular to the base surface (i.e. a gravitational plane), which results in an uneven load distribution on the adjusting wedge and an additional moment loading and stress on the screw spindle and/or the bearing, and additionally affects the stability of the levelling shoe.
A further disadvantage lies in the fact that the adjusting wedge displays a relatively complicated form (U-shape, precise seat surfaces and guidance surfaces, etc.). Especially when the levelling shoe is used for large heavy loads, for example, machine tools, which are also exposed to powerful changing loads, so that it is vital for the adjusting wedge to be extremely rigid, and the adjusting wedge must be manufactured precisely from steel, and thus the levelling shoe is expensive to produce.